Under normal, non-regenerative braking in a vehicle with a regenerative braking function, as the brake pedal is pushed by a driver, hydraulic pressure, generated by a master cylinder, is supplied to a wheel cylinder through a supply control valve, thus braking the wheel.
Under regenerative braking, the supply control valve is closed, and some of the brake fluid returns to an oil reservoir of the master cylinder through a return control valve, reducing the pressure in the wheel cylinder. When the pressure in the wheel cylinder reaches a desired value, the return control valve is closed.
One of two methods is typically used to additionally increase the pressure in the wheel cylinder during regenerative braking. The first is to reopen the supply control valve, which rapidly increases the stroke of the brake pedal and causes the pedal to sink. The second is to activate a hydraulic pressure pump using a motor, which causes operational noise of the motor and pump. The limited durability of the motor and pump are also concerns.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.